The present invention relates to a device for recording an image on a cathode-ray tube on a photosensitive thermal development recording medium with suitable density maintained at all times.
A photosensitive thermal development recording medium is one which is, after being subjected to image exposure by light, developed by being heated, for instance, at 100.degree. C. Such a recording medium is commercially available and sold under the trade name "DRY SILVER" made by Minesota Mining & Manufacturing Co. (3M Co.). In general, a photosensitive thermal development recording medium is suitable for producing a hard copy which can be readily and instantaneously developed. However, it suffers from drawbacks in that, before it is used, its stability over a period of time is low. That is, its sensitivity is considerably reduced if it is held at room temperature. For one particular photosensitive thermal development recording medium which has been tested, its sensitivity is reduced to about one-third if it is held at a temperature of 25.degree. to 30.degree. C. Therefore, the recording medium must be subjected to trial development several times in order to determine the exposure data to obtain the optimum density of an image.
In view of this, the invention relates to a device in which, in order to eliminate all of the above-described difficulties, an image of a density wedge used for determining the extent of sensitivity deterioration of a recording medium is optically projected onto the recording medium separately from the image on a cathode-ray tube. The identification step number, at which a density higher than the fog density is provided, of the density wedge developed is photo-electrically or visually determined whereby the exposure data of the image on the cathode-ray tube is corrected to perform recording with a suitable density. According to the invention, the recording can be achieved with a suitable density after carrying out the trial development only once.